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WorksheetsFORMATIVE ASSESSMENT 4: THREE PHASE MOTOR
Total questions: 15
Worksheet time: 12mins
a rotating magnetic field is created by :
applying three phase waveforms to rotor winding placed 120 degrees apart.
applying three phase line voltages to stator winding via sliprings
applying three phase line voltages to red yellow and blue stator windings.
applying three phase phase voltages to a delta connected load.
slip is defined as :
the difference between synchronous speed and rotor speed
the difference between rotor speed and synchronous speed
synchronous speed - rotor speed / rotor speed
(rotor speed - synchronous speed ) / synchronous speed
the rotor in an induction motor can :-
reach synchronous speed quickly
reach rotor speed slowly
always rotate close to the synchronous speed
can never reach synchronous speed
The rotating part of a motor is
Stator
Rotor
Frame
Bearing
The speed of a 50 Hz 3 Phase Induction Motor with 8 poles running with 2% slip is:
367.5 RPM
2940 RPM
735 RPM
15 RPM
How many poles does a 3 Phase Induction Motor have if it is supplied at 60 Hz, has a slip of 5% and runs at a speed of 1140 RPM
2
3
4
6
If a 3 Phase Induction Motor has 4 poles and is connected to a 60 Hz supply it has a synchronous speed of:
1500 RPM
750 RPM
900 RPM
1800 RPM
A three-phase, 50 Hz induction motor has a full load speed of 1440 rpm. The full load slip will be ____________%
3
5
4
2
If any two phases for an induction motor are interchanged
The motor will run in the reverse direction
The motor will continue to run in the same direction
The motor will stop
The motor will Burn
The data of 3-phase motor is called:
Motor price
Control circuit
Operating manual
Name plate
How many poles does a 3 Phase Induction Motor have if it is supplied at 60 Hz, has a slip of 5% and runs at a speed of 1140 RPM
2
3
4
6
The speed of a 50 Hz 3 Phase Induction Motor with 8 poles running with 2% slip is:
367.5 RPM
2940 RPM
735 RPM
15 RPM
S = (ns - nr) / ns, this formula refer to ?
rotor speed
slip of motor
stator speed
frequency of rotor
The formula for calculating synchronous speed is:
Ns= 120f/P
Ns= 120P/f
Ns= f/120P
Ns= P/120f
A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles in the motor is
2 pole
3 pole
4 pole
6 pole
